Secondary N-vinyl carboxylic acid amides can be polymerized to give water-soluble homopolymers and copolymers. Such polymerizations are disclosed in Gless, et al., U.S. Pat. No. 4,018,826. The N-vinyl carboxylic acid amides used in the polymerization can be obtained by removing an alcohol from N-(1-alkoxyethyl)carboxylic acid amides. Jensen, et al., U.S. Pat. No. 4,322,271 discloses a three-stage process for forming N-vinyl-N-alkyl-carboxylic acid amides starting from N-ethyl-carboxylic acid amides. The N-ethyl-carboxylic acid amides undergo anodic alkoxylation to form N-.alpha.-alkoxyethyl-carboxylic acid amides which are subsequently heated to split off an alcohol and form the final product. Stockman, et al. U.S. Pat. No. 4,554,377 discloses a process for preparing N-.alpha.-alkoxyethyl-carboxylic acid amides from dimethyl acetal and a carboxylic acid amide, and subsequently for the synthesis of secondary N-vinyl carboxylic acid amides therefrom.
While the above-described methods have been applied for forming secondary N-vinyl carboxylic acid amides, existing methods for the preparation of the starting materials; i.e., N-(1-alkoxyethyl) carboxylic acid amides are inefficient and impractical when applied on an industrial scale. Such methods for forming N-(1-alkoxyethyl) carboxylic acid amides include the electrochemical alkoxylation of N-ethyl carboxylic acid amides with alcohols. While the electrochemical processes do operate cleanly and in good yields, the operations are complex and recovery of the conducting salts is expensive.
Schmidt, U.S. Pat. No. 4,334,097 discloses a process for preparing N-.alpha.-alkoxylalkyl-carboxamides by reacting primary or secondary amides of aliphatic, araliphatic or aromatic carboxylic acids or cyclic carboxamides which are not capable of forming an aromatic system, with open-chain .alpha. halogenoalkyl ethers in the presence of tertiary amines. This process, however, requires the disposal of large quantities of acid salts.
Primary alkyl carboxylic acid amides react with acetaldehyde dimethyl acetal to give N-(1-methoxyethyl) carboxylic acid amides. This process requires large excesses of acetal; i.e., about 20:1; to achieve practical yields and purities, and is reported to fail for formamide. See R. W. Stackman, et al., Ind. Eng. Chem. Prod. Res. Dev. (1985), 24, 242-246.
Murao, et al., U.S. Pat. No. 4,567,300 and Great Britain equivalent 2 152 929 A discloses a process wherein acetaldehyde reacts with formamide in the presence of a weakly basic catalyst to yield solid N-(1-hydroxyethyl) formamide which, following catalyst neutralization, reacts with alcohols in the presence of an acid catalyst to yield N-(1-alkoxyethyl) formamide. This process is unattractive in that it requires two discrete steps, the handling of a solid intermediate, and the disposal of salts.
H. Bestian, et al., German Patent 1,273,533, discloses the synthesis of tertiary N-(1-alkoxyethyl) carboxylic acid amides from the reaction of acetaldehyde, alcohol, and secondary amide at 50.degree.-150.degree. C. using a 1.5-4 molar excess of acetaldehyde vs. amide.